Synthetic Oil-Yes/No

What are the , advantages/disadvantages, of useing synthetic oil to lubracate the engine of my pick-up? My vehicle is a '99 Chevy Siverado, the engine is the small V-8 (non diesel). When I whad the oil changed last ,was told that if I chose to replace the oil with synthetic the engine would run cooler and the interval between oil changes would increase, though I would not be able to go back to the petroleum oil in the future. Is that all there is?

I’ve heard this elsewhere but I’ve been skeptical. I have no personal expertise in the matter, but the Car Talk guys say it’s a myth:

I have heard this much more when synthetic oils first came out to market, I think it is mostly debunked. Some oils are synthetic blends, which contain dino oil as well as syn. oil. I have heard that it is OK to make your own syn. blend by using full syn. oil + dino oil poured in the crankcase.

As for if you will see any difference, in a 3.0 v-6 with over 100K miles in it I switched to full syn and notices a 2-3 mpg gain, in a 10K old 4 banger when I switched I didn’t notice any mpg improvements.

As for running cooler, I don’t know, could be and it makes sense.

I made the switch because of the high amount of miles I drive and want to extend the oil change interval as 3000 miles would sometimes be a oil change per month.

When I went in for synthetic oil, I asked about the longer change interval; admittedly it was the dealership telling me (who might have a vested interest in continued income), but two employees separately told me that the interval was the same for synthetic. OTOH, the guy changing it told me it protected better, and that I would ‘notice a difference’.

I’m not sure what he intended, but while my car has been reasonably smooth starting regardless of the temperature, my mileage has tanked from 550+ to 440 km/tank. (Though I noticed a slightly less drastic drop in mileage last year in the winter, so it might just be that).

I make detergent additives for motor oils. All of the oil manufacturers we supply to are of the opinion that synthetic and conventional motor oils can be interchanged freely.

Here’s Quaker State’s overview, which is pretty good; see Myth #4.

Most of the oil companies suggest that synthetic oils have superior performance to conventional oils. This is mainly reduced break-down, resulting in longer recommended oil change intervals. Experts still squabble over this one. I personally use synthetic, but if you’re changing your oil pretty regularly, it is not going to make much of a difference.

The only virtue of synthetic oils; they resist high-temperature breakdown better, and flow better at extreme low temps. Other than that, is it worth 5 X the price? Of course, if you have a turbocharged engine, you probably are required to use it. It is mostly profit for the oil companies-it costs them only about 25 cents (more)a quart to make the stuff. Question: what hasn’t the industry developed a silicone-oil based motor oil? that would probably last forever!

It’s possible that the silicone based oil wouldn’t stand up to heat.

I happen to work for an oil company, and yes, the oil itself is probably the cheapest part of what you get in the bottle. The rest is marketing and R&D. But remember that the majority of an oil company’s profits come from exploration and production, not from retail. Not to get into a long discussion about how oil markets work, but oil companies produce oil for cheap, then sell it at market rates (profit!). The refining and lubes divisions of those companies that use that crude have to buy it back at those market rates (otherwise the production folks wouldn’t make top dollar). Our retail divisions probably make the least profit.

Because, nowadays, the oil-change interval isn’t set by oil breakdown. It’s set by when you’ve used up the active additives in the engine oil – primarily, the acid-neutralization supplied by overbased detergents. Other components are eventually depleted, as well.

Even if there was some eternal, silicone-based lubricant, you’d still have to replace the detergent, dispersant, antioxidant, viscosity improver, etc. package in the engine lubricant. Top-treating can only extend the engine oil life for a short while, before the spent additives need to be removed. And when you do that, you might as well replenish the whole crankcase, both base oil and additives.

Synthetics also are less prone to forming engine sludge. Some autos, such as my dear old Audi–cough–had serious sludge issues. The nation’s Audi dealers (and Toyota dealers, IIRC) insisted that sludge was the result of infrequent oil changes, but in some cars it was a design problem.

Synthetics can prevent expensive, sludge-related engine repairs.

People who have cars that leak oil fairly bad sometimes say they don’t need to change their car’s oil, provided they keep the crankcase topped off. You’ve demonstrated why they are asking for trouble.

Another weird trend: Dealers are increasingly telling car buyers that they can skip changing the oil filter every other oil change. Why would someone sweat an additional $10, over something that might prove critical down the road?

Really, most oil filters have excess capacity. I believe that some manuals are speccing skipping the filter change for cost and environmental reasons. Most solids in the crankcase oil are well-nigh microscopic, and I suspect that it is reasonable.

Waste of money unless your car specs it, you run the oil for extended intervals or below negative 25 fahrenheit.
If you still want to do it, I suggest Pennzoil Platinum. It’s nice stuff, gives very low wear numbers in normal drain intervals, uses an innovative formulation, and has a pretty bottle.

A guy I know puts it this way “It’s like putting on the same underwear after you take a shower!” Not sure I agree though.

A new filter allows larger particles to pass than a used one that has some of the larger pores filled with “stuff”. So it is possible that reducing the filter replacement interval exposes the engine to a smaller abrasive load than frequent changes.

Go too long though, and the filter plugs up and starts bypassing. So there is a “sweet spot” and presumably the auto manufacturers have done research to determine what interval is optimal, while still providing a safety margin.

The concern over going back to mineral based oil after running synthetic is related to gaskets, seals, and other “rubber” parts first swelling with the synthetic, taking a set, then shrinking with the mineral based oil, resulting in leakage…NOT a concern that the engine would become “addicted” to the synthetic, and go through withdrawal on the regular oil.

Engines that need to start in bitter cold benefit greatly from synthetic, as it has a much lower pour point. It was a huge help in a BMW twin motorcycle I rode for a long time (airhead, weak starter/battery). Note: I wouldn’t run it in a bike with a wet clutch.

A second to those who noted “if your car’s engine requires it.” My husband decided that plain ordianry oil was good enough for our VW Passat. We had a highway breakdown and an expensive repair job – including flushing out the old oil – as a result. No problems since, as long as we keep using the synth.

Is there any appreciable difference between synthetic oils? MOBIL 1 is widely touted as the best-it seems just about every maker has its own brand, such as Penzoil, Quaker State, Castrol, etc.
Are they all pretty much the same?

Most of the general market synthetic motor oil blends are largely the same in terms of performance. Once they pass ILSAC or whatever certification, they’re optimized for cost. As a consequence, the additive packages all tend to look very similar – there might be some minor changes, slightly different detergent chemistry or VII chemistry used, but it’s all much of a muchness.

The higher-end synthetic blends, the “premium” stuff, will have more additives, and each oil company tends to have its own performance requirements above and beyond the standard for their “premium” oil. I don’t know enough on the performance results for most of 'em, and can’t talk about the performance data on the rest, so I’d say if you’re interested in a premium synthetic oil, to talk to your preferred mechanic and get his or her opinion.

As Aestivalis alluded to, the oil companies – Quaker State, Pennzoil, etc. – are mostly just supplying the base oil. The additives – which are the active chemistry in the motor oil, and where the R&D costs accrue from – are sourced from companies that specifically manufacture oil additives. The additive companies used to be part of the larger oil companies, but their profit margins are so much lower (because of the R&D costs, mainly) that they were essentially all spun off or joint-ventured. Consolidation in the industry has left 3-4 major additive producers, and a host of smaller, specialized additive producers. The oil companies purchase their additive package chemistry from the smaller additive companies, add their own base oils, and put it into bottles with their labels on them. So competing oil companies might be using chemistry that’s ultimately from the same source(s).

And it’s not easy on the additive companies – they buy their raw materials from the oil companies, and sell their products back to the oil companies. But from different divisions of the oil company, who all have their own profitability requirements, and so are interested in squeezing the additive company on cost and price. The additive companies also bear the costs of R&D, and of engine testing to pass certifications.

Our marketing VP has a lovely slide showing a quart of engine oil next to a quart of bottled drinking water – and their prices. Guess which one sells for less?

I’m sure some mechanics can tap an impressive data bank of empirically-derived knowledge, but many are among the most unscientific, anecdote-driven people I’ve ever met. Asking your garden-variety mechanic for a comparative analysis of high-temperature shear, NOACK volatility, cold cranking viscosities, thin-film oxygen uptake, etc. seems a bit much.

Re: not changing oil filters: Oil filter performance varies considerably–I’m talking wild variations–among manufacturers. Manufacturing in recent years has trended toward cheaper, less reliable internal parts. Some new filters have repeatedly been observed to bypass oil almost immediately after installation. Admittedly, I’m cautiously suspect of internal, in-house testing and am not aware of any reputable independent tester that has subjected all brands to exhaustive analysis, but spending an extra $10 every 4 months on a $30,000 to $60,000 automobile seems a prudent investment.

I have heard that the *primary * reason for changing your oil is *not * because the oil is full of particulates/dirt… it’s because the oil accumulates gasoline. Gas is not a good lubricant. Furthermore, your oil filter will not filter the gas from the oil.

While there may be a factual answer to your OP, I think this one is better suited to IMHO.


Here’s a good forum dedicated to motor oil: Bob is the Oil Guy

And some detailed research here: Motor Oil 101

I use Pennzoil Platinum 5W-20 with an oil change interval of 7500 miles and have been very pleased with the noticeably quicker starts, better fuel mileage, and overall smoother operation of the engine.

Advance Auto Parts had it on sale for buy one get one free, I think the sale runs through the end of January.

Here’s an interesting site regarding oil filters: Engine Oil Filter Study